I've had my computer for just over half a year and only had this problem for a few days. When I am playing Battlefield 3, sometimes after a certain amount of time (looks like between 30 min to an hour) my game would crash and I would get the blue screen of death. The blue screen would appear for a second or two, and then my computer would automatically reboot itself. I have uploaded my Windows/Minidump file for today which contains two crashes:

This never happens to any other games I've played (Crysis, Bioshock, Starcraft, Call of Duty...). I have not installed any new software on my machine for almost a month now. My computer is not over heating as my room today is fairly chilled.

if it isn't temperature problems look at your event viewer (Control Panel\System and Security\Administrative Tools\event viewer) for critical errors go from there . if you cannot find anything then you could also try different vid card drivers and if that doesn't seem to work maybe play around with your vid card voltages just bump up or down ever so slightly

Its not a temperature issue. I am monitoring my temps via Open Hardware and my GPU peaks at 75*C and CPU at 55*C.

I just increased my VCCSA voltage in my BIOS from auto to 1.107v. I'm still testing to see if that fixed my problem.

I checked my Event Viewer and I do see three critical errors that occured within the past 7 days marked as "Event ID 41 Kernel-Power" and "Task Category 63". The note associated to this is "The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly."

In addition, just earlier, in the middle of gaming, I received a black screen with white text (like in command prompt) saying "Reboot and select proper boot device or insert boot media in selected boot device and press a key". This screen appeared when I alt+tabbed out of my game. Windows hung for a few minutes (like it froze), and then my screen suddenly became black with that text. I turned off my computer and left it alone for a few hours. Upon turning it back on, I did not see that error message.

sounds almost like there is something running in the back ground while you are running the game, I would check to see which process's are running while the game is running check for any cmd prompt or anything else unusual

if this was a non legit game I would say that you have a trojan that only runs when the game is running. way back I used to use a script that would auto set my reg so tha tthe least amount of things where running on my PC then it would reboot my PC and start up ET so that I only had 15 process's running + the game and team speak.